Optically detected magnetic resonance study of defects in undoped, Be-doped, and Mg-doped GaN

Undoped, Be-doped, and Mg-doped GaN samples were investigated with photolum inescence-detected electron paramagnetic resonance (PL-EPR) and electron-nu clear double resonance (PL-ENDOR). Two types of shallow donors and a deep l evel Be-related complex were measured in Be-doped GaN. One type of shallow donors is probably due to Si contamination. In all investigated samples, di stant gallium ENDOR lines were observed which were split by a quadrupole in teraction. From this splitting the electrical field gradients (efg's) at th e Ga nuclei in all investigated samples could be determined very precisely. The efg's were correlated with strain.